1. Field of the Invention
The present invention relates to optical disc drive apparatuses and camera apparatuses in which the tilt of a light beam can be controlled in accordance with skew occurring in an optical disc by using an angular velocity sensor configured to detect the angular velocity applied to the optical disc that is rotating. The present invention also relates to methods for controlling the tilt of a light beam in accordance with skew occurring in an optical disc by using an angular velocity sensor.
2. Description of the Related Art
Optical disc drive apparatuses perform recording and reproduction of information, in which a light beam (LB) emitted from an optical pickup is applied to an optical disc while the optical disc is rotating rapidly. In this operation, focus control and tracking control of the optical pickup are accurately performed so that the light beam (LB) emitted from the optical pickup is accurately applied to tracks provided on a signal recording surface of the optical disc. However, when an external force is applied for some reason, skew may occur in the optical disc. If the amount of skew exceeds a predetermined tolerance, it becomes difficult to realize accurate application of the light beam, leading to interruption of recording and reproduction. Therefore, it is desired to provide a preventive measure.
To prevent the occurrence of skew, an operation for correcting a relative angular shift of the optical pickup (or an objective lens thereof) with respect to the optical disc, namely tilt control, is desired to be performed. There are two kinds of tilt control: a method in which the objective lens is tilted, and a method in which the entirety of the optical pickup is tilted.
To perform tilt control, it is desired to detect the amount of tilt (skew) in the optical disc. There are various exemplary methods for such detection.
For example, Japanese Unexamined Patent Application Publication No. 2001-43605 discloses an optical disc drive apparatus in which a measuring beam is applied to an optical disc from an optical component called a tilt sensor, which is provided separately from an optical pickup, and the tilt of the optical disc is detected from a shift in the reflected beam position, whereby a skew value is obtained.
Japanese Unexamined Patent Application Publication No. 11-339371 discloses another exemplary optical disc drive apparatus in which detection of the skew value is performed by using a monoaxial angular velocity sensor. This optical disc drive apparatus employs a control method in which the monoaxial angular velocity sensor calculates the skew (radial skew) in the optical-disc radial direction in which an optical pickup is movably disposed, and, if skew exceeding a skew margin occurs, recording is stopped.